[Gdal-dev] Re: how to read SRTM files - conclusion!

[Eduardo Patto Kanegae]

Hi folks,

I'd like to thank everybody for replies contribution... This show us how 
powerfull Free Software philosophy can be. 'Cause it's only about 
software, it's about to share data and knowledge.

Now, I'm going back to my SRTM task because I have more than one 
option/suggestion to do an only job.

Thanks all. I pasted all replies below!

Eduardo Patto Kanegae
http://www.webmapit.com.br
Treinamento & Consultoria em UMN MapServer e FreeGIS Software
ICQ: 303747254
MSN: eduardo_patto~at~hotmail.com
+55(16)9994-2928

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Markus Neteler escreveu:

  Eduardo,

you can use GRASS 5.7-CVS also, I have recently 
integrated r.in.srtm.

Markus



Mario Beauchamp escreveu:

  Hi,

On Mon, 13 Dec 2004 18:41:36 +0000, Eduardo Patto Kanegae <lists at webmapit.com.br> wrote:


  

>I'm downloading SRTM NASA ziped files from 
>ftp://e0dps01u.ecs.nasa.gov/srtm/South_America/ but I saw that I don't 
>know this file format(.hgt)
>  
>

You can also get SRTM data in Geotiff format from 
ftp://ftp.glcf.umiacs.umd.edu/glcf/SRTM/

And you have the choice between WRS2 and degree tiles.
--
Mario B.
Landsat images (demo):
http://pages.infinit.net/starged/landsat/home.htm



Eliseo Cantellano escreveu:

  Eduardo.
You can use Global Mapper, also.

Eliseo Cantellano
National University of México


Ethan Alpert escreveu:

  
Looks like you're grabbing the "unfinished" data. 

>From the Documentation directory:
ftp://e0dps01u.ecs.nasa.gov/srtm/Documentation/QuickStart.txt

"Height files have the extension .HGT and are signed two byte integers.
The
bytes are in Motorola "big-endian" order with the most significant byte
first,
directly readable by systems such as Sun SPARC, Silicon Graphics and
Macintosh.
DEC Alpha and most PCs use Intel ("little-endian") order so some
byte-swapping
may be necessary. Heights are in meters referenced to the WGS84 geoid.
Data
voids are assigned the value -32768."

You're going to need to do some processing before you can use these
files.

-e




Ben Discoe escreveu:

Eduardo,

Or, simply drag your .hgt files into some nice GDAL-based software such as
VTP's VTBuilder, which will automatically recognize the .hgt and load it
directly.

-Ben
http://vterrain.org/



Thom DeCarlo escreveu:

Eduardo,
This question has come up quite a few times in several lists I'm on. (I
asked once, myself.)

First, if you are using a Linux computer or can install Cygwin (from
www.cygwin.org) on your Windows computer you can use this bash script that I
modified from Markus Neteler's website:
http://mpa.itc.it/rs/srtm/

This shell program will change the name of the .hgt to .bil. It then
generates the .hdr and .prj files for the ESRI file reader. Finally, it
launches gdal_translate to build a geotiff from the bil file.

HTH,
Thom


Thom DeCarlo
---------------------------------------------------------
    Do Not Meddle in the Affairs of Dragons
For You are Crunchy and Taste Good with Ketchup



Vincent Schut escreveu:

There has been some postings on this list before about this topic. A google 
search on 'gdal srtm' will probably give you these.
Shortly, the hgt files are simple binary data, but can easily be 'translated' 
into a BIL file (which can be opened by GDAL) by generating the apporpriate 
(text file format) header file. You will find the exact answer on how to do 
this in the earlier postings on this list.

Good luck!

Vincent.

On Monday 13 December 2004 21:54, Ethan Alpert wrote:

>Looks like you're grabbing the "unfinished" data.
>
>>From the Documentation directory:
>
>ftp://e0dps01u.ecs.nasa.gov/srtm/Documentation/QuickStart.txt
>
>"Height files have the extension .HGT and are signed two byte integers.
>The
>bytes are in Motorola "big-endian" order with the most significant byte
>first,
>directly readable by systems such as Sun SPARC, Silicon Graphics and
>Macintosh.
>DEC Alpha and most PCs use Intel ("little-endian") order so some
>byte-swapping
>may be necessary. Heights are in meters referenced to the WGS84 geoid.
>Data
>voids are assigned the value -32768."
>
>You're going to need to do some processing before you can use these
>files.
>
>-e
>  
>


Eduardo Patto Kanegae escreveu:

> Hi folks,
>
> I'm downloading SRTM NASA ziped files from 
> ftp://e0dps01u.ecs.nasa.gov/srtm/South_America/ but I saw that I don't 
> know this file format(.hgt)
>
> runnig "gdalinfo" one .hgt file I only got:
>
> ERROR 4: `N01W050.hgt' not recognised as a supported file format.
>
> GDALOpen failed - 4
> `N01W050.hgt' not recognised as a supported file format.
>
> Or my GDAL tools is missing something?
>
> Is there any free software that can read this files?
>
> thanks
>
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